Tiered link building uses two levels of backlinks to boost your site's ranking....

https://www.mediafire.com/file/z9mgvqdwwo1eb8a/pdf-42897-77316.pdf/file

Tiered link building uses two levels of backlinks to boost your site's ranking. Tier 1 links point directly to your site from quality sources. Tier 2 links support those Tier 1 sites, helping improve their authority